The invention relates to a control circuit for generating two control currents for a variable gain amplifier having a gain which is substantially proportional to the ratio of the two control currents. Variable gain amplifiers (VGA) with a gain proportional to the ratio of two currents are known from European Patent Application 0 582 365, which shows techniques known from U.S. Pat. No. 3,849,735, which in turn shows techniques known from a paper by B. Gilbert, "A New Wide-Band Amplifier Technique" , IEEE Journal of Solid-Sate Circuits, Vol. SC-3, No. 4, Dec. 1968, p. 353-365. Such variable gain amplifiers exhibit a large bandwidth and can be used, for example, in read amplifiers for hard disk drives in which a variable gain is needed to compensate for the fluctuating output signal of the read head. For this purpose an automatic gain control (AGC) loop is incorporated in the signal processing chain in order to have a constant signal level. In order to get an AGC performance which is independent of the level of the input signal, an exponential VGA control is needed, i.e. the gain should be proportional to exp(x), where x is the control parameter. This means that the ratio of the two control currents for the VGA should be exponentially proportional to the control parameter.